1. Field of the Invention.
This invention relates to roller braking devices and more particularly to such a device for use in a roller assembly for loading and unloading cargo in a vehicle.
2. Description of the Related Art
Roller devices for use in loading and unloading cargo on the floor of a vehicle such as an aircraft or a truck are well known in the art. The rollers are often mounted on a track attached to the vehicle floor such as shown in U.S. Pat. No. 4,462,493 issued to Nordstrom on Jul. 31, 1984. When such rollers are employed it is necessary to provide a mechanism for retaining the cargo in the loaded position. This end result can be achieved by lowering the wheels below the floor as described in U.S. Pat. No. 4,823,927 issued Apr. 25, 1989 to Jensen.
While unloading or loading cargo, some braking action is generally needed to restrain the cargo against free motion along the floor when the rollers are in their raised position. This is particularly necessary where the vehicle floor is on a slant, as in the case of most aircraft. U.S. Pat. No. 4.,089,389 issued May 16, 1978 to Webb describes the use of stop plates for achieving this end result. Other approaches include the use of a viscous fluid within a braking roller and the use of sliding friction surfaces in the roller. The use of viscous fluid has the disadvantage of the danger of leakage while approaches using sliding friction and stop plates have the shortcoming of the wear and tear on this elements which requires replacement more frequently than to be desired.
The system of the present invention utilizes braking rollers which are mounted on the vehicle floor, to provide resistance to the movement of the cargo in one direction and permitting free movement in the opposite direction. A plurality of such braking rollers may be used, some oriented to provide resistance to motion in one direction, others oriented to provide resistance to motion in the opposite direction (or any other direction as may be needed). Each braking roller has a central hub which is supported on unidirectional bearings such that the central hub of the roller is free to rotate in one direction but locked against rotation in the opposite direction. The central hub is mounted for rotation on a fixed shaft.
The outer wall of the central hub is covered with an elastomer. The roller has an outer cylindrical wall on which the cargo rides. The opposite ends of the cylindrical wall have end covers between which a plurality of rods are supported for rotation on the central shaft on bearings. These rods abut against the elastomer with sufficient pressure to deform the elastomer and provide braking action . The outer wall is thus coupled to the central hub and will rotate therewith when the central hub is free to rotate(i.e. in one direction). The roller is free to rotate in one direction. In the opposite direction, the unidirectional bearings prevent the central hub from rotating. The hub outer wall, however, carries the rods around along the elastomer which is deformed by the shafts and thus while rotation is permitted there is resistance against such rotation.
It is therefore an object of this invention to provide an improved brake roller for providing resistance against the motion of cargo along roller wheels during the loading and unloading of cargo.
It is a further object of this invention to provide a brake roller for use in loading and unloading cargo along roller wheels which is of more economical construction than prior art devices.
It is still a further object of this invention to provide a brake roller for use in loading and unloading cargo along roller wheels which is more durable than prior art devices.
Other objects of the invention will become apparent in view of the following description taken in connection with the accompanying drawings.